A fluid pressure device such as a vacuum generating unit is constructed by connecting together a plurality of blocks having different functions, and which are provided respectively with peripheral devices such as a feed valve for supplying either vacuum or compressed air, a vacuum break valve, an attraction confirmation switch serving as a vacuum detecting means, a timer, a display, etc. Further, electrical mechanisms are electrically connected to a control device such as a sequencer or the like by signal conductors or wires, such as discrete lead wires or the like, to thereby transfer control signals therebetween.
A vacuum generating unit according to the prior art is shown in FIG. 1. FIG. 1 shows a structure for connecting signal wires between a vacuum generating device 2 and a sequencer 4 which serves as an external device, in which ejectors respectively having different vacuum attracting or sucking conditions are set as vacuum generating sources. The vacuum generating unit 6a is constructed by connecting peripheral devices such as a compressed-air feed valve 12a, a vacuum break valve 14a, an attraction confirmation switch 16a, etc. to a block 10a having an ejector provided thereinside and a vacuum port 8a. The vacuum generating unit 6a, and other vacuum generating units formed in a manner similar to the vacuum generating unit 6a, are placed on a manifold 18 to thereby form the vacuum generating device 2. Compressed air is supplied from an unillustrated compressed-air feed source to the vacuum generating units 6a through 6e through a compressed-air feed port 20, so that negative pressures are generated by the ejectors respectively. In the vacuum generating units 6c through 6e, for example, negative pressures are supplied respectively from vacuum ports 8c through 8e to corresponding suction pads 24c through 24e through vacuum tubes 22c through 22e. Thus, the suction pads 24c through 24e attract and feed workpieces 26c through 26e.
The sequencer 4 has input keys 28 and a display unit 30 comprised of an LCD, both provided on an upper surface thereof. Further, the sequencer 4 has signal terminals 32 respectively connected to objects to be controlled.
The peripheral devices of the vacuum generating units 6a through 6e provided on the manifold 18 are separately connected to the signal terminals 32 of the sequencer 4 by a plurality of signal conductors or wires 34.
The vacuum generating device 2 is electrically connected to the sequencer 4 used as an external device by a plurality of signal wires 34 as described above. The compressed-air feed port 20 and the vacuum ports 8a through 8e are firmly connected to the peripheral devices through vacuum tubes 22a through 22e, so as to withstand the pressure of compressed air and the negative pressure. Further, the compressed-air feed port 20 and the vacuum ports 8a through 8e serve to keep the device airtight.
Thus, when it is desired to change the performance or functions of the vacuum generating device 2 according to a desired purpose at a job site, or to entirely replace one or more of the vacuum generating units 6a through 6e due to a sudden malfunction or the like at the job site, it becomes cumbersome to make such changes and much time is wasted. Particularly, an inconvenience is developed in that the procedure for releasing and re-connecting the plurality of signal wires 34 and the vacuum tubes 22a through 22e is cumbersome and requires a lot of time, and mistakes such as a misconnection of signal wires, etc. can arise.
Further, when the units are rearranged or replaced, the pressurized-fluid passage which communicates with the entire vacuum generating device 2 is opened thereby discharging pressurized fluid to the outside and drawing air into the passage. Therefore, the replacement or rearrangement work can only be performed after the process of attracting and feeding of a workpiece by the vacuum generating device 2 has been completely discontinued. Accordingly, work efficiency is greatly reduced.
Moreover, when the units are recombined, dust or the like enters into the vacuum generating device 2 due to the suction of air from the vacuum passage, so that a reduction in performance occurs since the airtightness of the device is lowered after such recombining work has been carried out.
On the other hand, the sequencer 4 manages or controls all of the signal wires 34 for the peripheral devices making up the vacuum generating units 6a through 6e, and internally controls the timing for each of the peripheral devices.
Thus, the number of the signal wires 34 electrically connected between the peripheral devices of the vacuum generating units 6a through 6e and the sequencer 4 greatly increases. Hence, it is cumbersome to provide wiring for the signal wires 34, miswiring tends to occur. Further, the peripheral devices can experience malfunctions due to noise or the like generated between the signal wires 34. Such an inconvenience is also common even with other vacuum units connected to the sequencer by a plurality of signal wires, as well as to the vacuum generating units.
It is therefore an object of the present invention to provide a fluid pressure device capable of easily carrying out, at a job site, either the rearrangement of the fluid pressure device according to desired functions and performance thereof, and to facilitate the replacement of the fluid pressure device when sudden malfunctions or accidents occur, without discontinuing the general operation of a working line using the fluid pressure device, and further avoiding a reduction in performance of the fluid pressure device after either its rearrangement or replacement has been performed.
It is another object of the present invention to provide a fluid pressure device wherein complicated wiring, occurrence of miswiring, and malfunctions of the fluid pressure device due to noise can be avoided, by simplifying signal wires using an interface block and a serial transmitting means, and wherein the structure of the fluid pressure device can be reduced in size and weight, so as to improve its general-purpose properties.